The invention relates generally to a method and apparatus for filling vessels and more particularly with simultaneously and automatically filling a plurality of flexible pipette type containers or vessels with a liquid to precise levels through a small peripherally locating opening.
In many applications the filling of containers or vessels is carried out by the simple expedient of pouring the liquid into the container. Where controlled flow utilization is desired, a cover may then be affixed to the container, the cover containing a small outlet which is provided with either a valve, cap, or replaceable insert for resealing the container. Where, however, for functional or economic reasons, the container must be made in a single integral flexible piece, but with a small opening for controlled flow, the filling is obviously not so simple, since relief must be afforded for the air which the liquid will displace during the charging process.
There are, however, many applications for flexible vessels or pipettes which have small filling and discharging ports which are, or can be, formed by tubes of small diameters. These vessels can find particular utilization in medical, clinical and laboratory test applications. These flexible vessels can be squeezed to discharge the liquid from the vessels. The flexibility of the vessels is vital to the end use of the vessels or ampules to facilitate vacating the contents of the ampules by simply compressing the sides of the ampules. The vessels can be disposable or resealable for further use.
Because of the small ports, the filling of the vessels can be very tedious and time consuming. One method of filling this type of vessel is to insert a needle into the port and/or tube and to fill the vessel with liquid through the needle. This is only a partial solution to the problem since the liquid is injected into the opening with sufficient needle play to allow the air to escape. The container may, on the other hand, be directly charged or filled without a needle if an air escape is provided elsewhere in the container. Neither solution is completely satisfactory. In the former, the needle must be fairly fine; its dimensions, of course, being dictated by the diameter of the container opening. With fine bore needles, this leads to an excessively slow liquid flow rate. Further, with this arrangement, one must be prepared to meet the high cost inherent in precise positioning jigs and adjunct equipment, and the needles must be periodically flushed and carefully maintained.
The latter or direct filling method is also unsatisfactory because the air escape hole must be subsequently plugged or sealed, thus adding to the cost of charging. Again, the precise positioning of the container opening with respect to the charging apparatus raises the cost of the equipment and its maintenance. Both of these methods require that the vessels be handled one by one or by very complex machinery if filling by an automated system.
One solution is to vacuum fill the container by placing them in a vacuum chamber along with the liquid to fill the containers. The container opening is immersed into the liquid and the chamber and container are first evacuated and then the chamber is vented which forces the liquid into the containers or vessels. Such vacuum filling systems are generally well known, such as disclosed in U.S. Pat. No. 3,282,306. These systems do not, however, provide for automatically filling a plurality of the vessels with a minimal amount of handling.
Prefilled flexible pipette ampules could increase the accuracy of medical, clinical, laboratory and home testing by reducing the potential for human error for each test. Vacuum filling could produce very accurate filling of the vessels at a greatly reduced cost by automatic loading and filling a plurality of the vessels simultaneously. Additional cost savings then could be realized by the user by eliminating costly metering for each test. Additionally, the tests can be accurately conducted by a layman broadening the potential use of this type of product. Further, by eliminating the need for a skilled professional, tests can be conducted in the home or other non-laboratory settings or in field emergency situations.
Therefore, there is a need for a method and apparatus of simultaneously and automatically filling a plurality of flexible vessels with liquid to a precise level with a minimum amount of handling and complex machinery.